1. Field of the Invention
This invention relates to a magnetic tape cartridge, and more particularly to a magnetic tape cartridge comprising a cartridge casing and a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation.
2. Description of the Related Art
There has been known a single reel magnetic tape cartridge, comprising a cartridge casing and a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation, as a recording medium for an external storage for a computer and the like. Such a single reel magnetic tape cartridge is used for retaining important data of a computer or the like and accordingly is arranged so that trouble such as tape jamming does not occur and the magnetic tape is not accidentally drawn out.
The reel is provided with a cylindrical reel hub having a closed bottom and stopper gear teeth formed in a circle and a brake member provided with a brake gear which is adapted to be brought into engagement with the stopper gear teeth disposed to be movable in the direction of thickness of the cartridge casing along the axis of rotation of the reel. The brake member is urged, for instance, by a coiled spring toward a position where the stopper gear teeth are engaged with the brake gear to prevent rotation of the reel when the magnetic tape cartridge is not used. When the magnetic tape cartridge is loaded in a recording and reproducing system, a brake release spindle of the recording and reproducing system pushes upward the brake member to disengage the stopper gear teeth from the brake gear.
However if a space is formed between the brake member and the reel hub when the brake member is moved upward, dust and dirt can enter the inside of the cartridge casing through the space.